Virtual Poster Session

Welcome to the Virtual Poster Session, a new and powerful tool for networking and information exchange. Here you can share your work, search though the poster library, and start a dialogue with others in your field. Each uploaded poster that pertains to force measurement and testing can currently be used to apply for an academic travel scholarship; please see the Scholarships page for application details and deadlines.

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Submitted by Lauren Schroeder

Lateral ankle sprains, caused by rapid ankle inversion, and noncontact anterior cruciate ligament (ACL) knee injuries, caused by excessive knee loading, are among the most common lower extremity injuries that occur during dynamic tasks, such as cutting. Ankle braces are commonly used to prevent lateral ankle sprains by reducing ankle inversion. There is limited and conflicting research about how an ankle brace affects other joints, such as the knee, during cutting movements. It is also not known if sex differences exist during a cutting task when an ankle brace is present. The purpose of this study was to determine the effects of an Ultra Zoom® hinged ankle brace and sex on ankle and knee biomechancis during a cutting maneuver. Eighteen recreationally active adults completed sidestep cutting trials with and without an Ultra Zoom® ankle brace. Three-dimensional ankle and knee kinematics and GRF were collected. Separate 2×2 (sex × brace) repeated measures ANOVAs were used. Results indicated the brace reduced frontal plane ankle kinematics and had no effect on knee kinematics. Additionally, females demonstrated decreased knee flexion compared to males. An ankle brace during a cutting maneuver restricted frontal plane ankle movement. Furthermore, the only significant changes in knee mechanics were due to sex differences, which has been well documented. These findings indicate that the use of an Ultra Zoom® hinge brace is suitable for sports, reduces the risk of lateral ankle injuries, and does not alter knee mechanics, and therefore may not increase the risk of ACL injury.

Submitted by Stephanie Cone

Robotic testing was performed with a 6-degree of freedom load cell in order to analyze functional contributions of the soft tissues in the knee under physiologically relevant loading conditions. Age groups ranging from 1.5 months to 18 months, porcine equivalent to early youth through late adolescent human ages, were studied. Complete ACL transection resulted in increased APTT and VVR across all ages (p<0.05), while injury to the AM bundle did not affect APTT or VVR. Additionally, increasing age resulted in decreased APTT normalized to the tibial plateau (p<0.05) and an average 19° decrease in VVR across states from 0 to 18 months of age (p<0.05). The ACL was the primary restraint against anterior drawer in the intact knee state [75-111%]. Following AM bundle dissection, the PL bundle carried the vast majority of the anterior load regardless of age [66-112%]. Following complete ACL transection, the MCL and medial meniscus carried most of the force across ages under anterior drawer. The LCL contributed increasing resistance to varus torque across states with age, as did the MCL under valgus torque.

Submitted by Mark Olsen

INTRODUCTION: Clinical interventions for foot injury prevention are often prescribed based on static measures of foot structure. However, this convention merits further investigation as the static-dynamic relationship has only been explored in walking and running. The primary aim of this study was to explore the relationship between static foot structure and dynamic midfoot kinematics and kinetics during a barefoot single-leg landing.

METHODS: 48 females (age=20.4±1.8 yr, height=1.6±0.06 m, weight=57.3±5.5 kg) completed the study. Standing arch height index (AHI) was measured using the Arch Height Index Measurement System. Skin markers were attached using a multi-segment foot model by Bruening et al.1 A14-camera motion capture system (Vicon) was used to sample kinematic data at 250Hz while two force platforms (AMTI) sampled kinetic data at 1000Hz. A static trial was captured then subjects hung from wooden rings and performed barefoot single-leg drop landings from a height of 0.4m. Metrics were calculated in Visual 3D (C-motion, Inc.) to obtain static midfoot angle (MA), midtarsal range of motion (ROM), and midtarsal work. PCCs were calculated for static and dynamic variables using paired t-tests in SAS.

RESULTS: AHI was correlated negatively with sagittal plane midtarsal ROM (r=-0.32032, p=0.0264) and positively with midtarsal work (r=0.33180, p=0.0212). MA was correlated positively with sagittal plane midtarsal ROM (r=0.48336, p=0.0005) and negatively with midtarsal work (r=-0.32321, p=0.0250).

DISCUSSION/CONCLUSION: Static foot structure may be a valuable clinical tool in assessing midfoot function relating to injury risk in athletes, who participate in high-impact loading activities, as well as in pathological populations.

Submitted by Shelby Peel

Research has shown decreases in dorsiflexion ROM appear to be predictors for non-contact ACL injuries during landing tasks. The gastrocnemius-soleus complex (GSC) plays a critical role in dorsiflexion ROM, with a less compliant GSC decreasing dorsiflexion ROM. However, it is unknown whether acute GSC stretching can decrease ACL loading during landing tasks. Fifteen active participants completed three trials of single-leg drop-landings from a box. 3D-lower extremity kinematics and kinetics were captured using 3D-motion capture system and force plate. Between assessments, all participants completed a three-minute bout of stretching targeting the GSC. Musculoskeletal modeling was used to estimate ACL loading in the sagittal, frontal, and transverse planes, overall peak ACL loading, and time to peak ACL loading. Pretest and posttest ACL loading variables were compared with paired t-tests (p≤0.05). No significant differences were found between pre-stretch and post-stretch peak ACL loading time, peak frontal plane ACL loading, and peak transverse plane ACL loading (p>0.05). However, post-stretch peak sagittal plane ACL loading was significantly higher compared to pre-stretch peak sagittal plane ACL loading (p=0.008). Furthermore, overall post-stretch peak ACL loading was significantly higher compared to overall pre-stretch peak ACL loading (p=0.022). As the gastrocnemius plays a role in knee flexion, it is possible that an acute bout of stretching may increase gastrocnemius compliance, therefore increase in sagittal plane ACL loading. An increase in sagittal plane loading would also lead to an overall loading effect on the ACL. Future studies warrant investigation into the effects of chronic GSC stretching on ACL loading.

Submitted by John DeLucca

Residual stresses are known to exist in human intervertebral discs but have not been incorporated in finite element models. A multigeneration model was applied to the annulus fibrosus of the intervertebral disc to simulate residual stresses arising from growth and remodeling. The intervertebral disc shape and compressive creep were used to verify that the multigeneration approach generates realistic values of residual stress. The model was then validated by comparing its 6 degree-of-freedom mechanical response to experimental data. Human intervertebral discs were tested in a custom-built hexapod in all 6 degrees-of-freedom (lateral shear, anterior-posterior shear, torsion, bending, flexion, and compression). Incorporating residual stresses resulted in a finite element model which can predict 4 degrees-of-freedom while excluding residual stresses produces a finite element model that can only predict 2 degrees-of-freedom.

Submitted by Kyle Meadows

Disc function is mechanical, and measures of disc mechanical function are important to address spine function, degenerative disc disease, and low back pain. In vivo measures of disc mechanical function are needed, however the current standard in disc imaging is to acquire a single static image and classify the disc’s appearance using qualitative integer scales for degree of degeneration. Current grading standards are acknowledged as insufficient to identify symptomatic discs for treatment. In addition, static T2 weighted MRI cannot provide mechanical function information – mechanics must be measured as the change following a load or deformation perturbation. Because the disc experiences significant compression and height loss throughout the day, and because flexion-extension postures are often associated with low back pain, these physiological mechanical perturbations have potential to be used to quantify disc mechanics in vivo. The objective of this study was to use MRI-based methods to quantify in vivo disc function by measuring changes in disc geometry and T2 relaxation time with diurnal changes and with controllable posture. Quantification of in vivo disc mechanics by using diurnal loading or prescribed posture changes has potential to improve our ability to identify, evaluate, and treat degenerative disc disease. Symptomatic discs may have aberrant mechanics; if so, in vivo measurements of mechanical function may, with continued development, facilitate diagnosis of pathological discs.

Submitted by Danial Sharifi Kia

Knowledge of ligamentous contributions to joint stability is essential to restore normal joint range of motion and functionality through reconstruction procedures. Although, there has been numerous studies on the pathomechanics of the elbow joint, there have been very few rigorous and systematic attempts to characterize the roles of soft tissues during clinically relevant motions.
Five fresh frozen cadaveric elbows from three male subjects were used for this study. In-vitro simulations were performed using a VIVO six degree-of-freedom (6-DOF) joint motion simulator (AMTI, Watertown, MA) capable of virtually simulating the effects of soft tissue constraints (virtual ligaments). This study introduces a unique, hybrid experimental-computational technique for measuring and simulating the biomechanical contributions of ligaments to elbow joint kinematics and stability. In vitro testing of cadaveric joints is enhanced by the incorporation of fully parametric virtual ligaments, which are used in place of the native joint stabilizers to characterize the contribution of elbow ligaments during simple flexion-extension motions using the principle of superposition.
our results demonstrate the importance of AMCL and RCL structures as primary stabilizers under valgus and varus loading respectively. Virtual ligaments demonstrate the ability to restore the VV stability of the joint in the absence of any soft tissues attached to the osseous structures. This demonstrates the effectiveness of “virtual” ligaments for in vitro testing of elbow joint biomechanics, with applications in pre-clinical assessment of elbow implants.

Submitted by Devan Groulx

Lateral ankle sprains are common orthopedic injuries and often result in chronic ankle instability (CAI). Studies have shown that the CAI population typically has decreased ankle proprioception and possibly a greater reliance on visual feedback when compared to healthy controls. However, little is known about how the postural control characteristics change in those with and without CAI when external visual feedback is manipulated. Purpose: To compare postural control characteristics of persons with CAI, Copers and healthy adults when performing a single leg balance test with and without external feedback. Method: The definition for CAI used for this study includes persons who have experienced recurrent ankle sprains, in addition to self-reported “feelings of instability” and “giving way,” and a score on the Identification of Functional Ankle Instability (IdFAI) of 11 or greater. 18 participants with CAI, 15 Copers, and 18 healthy controls (mean age of all groups: 22 years) performed the Athlete Single Leg Test on the Biodex Balance System (BBS) at Level 4 which involved a high degree of platform instability. All participants completed 2 trials without and with feedback in that order. Center of pressure position was recorded and the two trial mean was used for further analysis. Overall stability index (OSI) defined as the mean distance of the center of pressure from the center of the platform was obtained from the system. Sway area was calculated using custom Matlab script. Separate 3 (Group) x 2 (Feedback) mixed ANOVAs were run using overall stability index (OSI), and sway area as dependent variables. Results: Significant feedback main effect showed participants had significantly lower (better) OSI value with feedback (1.4±0.1) compared to without feedback (2.6±0.2; P < 0.001) but sway area with feedback (8.61±2.33cm2) was similar to without feedback (10.94±2.43 cm2). There was no significant group main effect or interaction observed for either of the variables. Conclusion: Results suggest that external visual feedback may not play a significant role in helping persons with CAI improve their postural control.

Submitted by Emily Messerschmidt

Title:  Head Acceleration During Girls Youth Soccer Using Real Time Data
Emily Messerschmidt, Katlyn Van Patten, Ryan Lee, Srikant Vallabhajosula

Purpose/Hypothesis: While the acute effects of concussion have been the focus of research in the past, there is a new emphasis toward following the cumulative effects of sub-concussive head accelerations in athletics. This is especially important in youth athletes because the developing brain is more vulnerable to injury from head trauma in sports like soccer due to techniques such as heading, that can result in numerous head impacts throughout play. There is a current lack of evidence on the magnitude and frequency of head accelerations that occur during real-time youth sports, including soccer, and whether these accelerations have a detrimental cumulative effect. The purpose of the current study was to measure the head acceleration that youth athletes experience during real-time soccer games.
Number of Subjects: 31 under-15 girls club soccer participants. 11 players monitored each game.
Materials/Methods: 3 season games were observed. Triax Smart Impact Monitor headband accelerometers were worn during gameplay to collect real-time head impact data. Forces >10g were recorded. Games were video recorded for further analysis. Head impacts were categorized by type of impact: purposeful header (PH), player to player (PP), player to ground (PG), and ball to head (BH). Data was analyzed using descriptive statistics.
Results: A total of 171 impacts were observed (PH=20, PP=113, PG=36, BH=2). Only one impact recorded was above the concussion threshold of 70g. The majority (77%) of impacts observed were <10g. Of the accelerations recorded, PH resulted in the largest average acceleration (36.8±14.9g) followed by PG (20.5±4.2g), and PP (19.5±4.6g). The maximum accelerations for PH, PG and PP were 73g, 26g and 30g respectively. No BH accelerations were recorded >10g.
Conclusions: While PH yielded the highest average acceleration, it was one of the least frequently occurring impacts. PP impacts were most common however the majority produced little to no head acceleration. While there was variability of head acceleration that occurred within each type of impact, none produced consistently dangerous (≥70g) accelerations.

Clinical Relevance: This study provides preliminary evidence of the impacts sustained during girls youth soccer games for athletic trainers or sports physical therapists who are monitoring athletes for concussions. The findings reveal that the use of headband accelerometers to measure real-time data can be a useful tool to monitor multiple players on the field. There remains a need for further research into the effect of cumulative sub-concussive impacts during soccer in youth athletes with larger sample size. Further studies should investigate the impacts players sustain over multiple seasons to observe if those who experience multiple sub-concussive impacts report concussion-like symptoms or show concussion-like signs. Additionally, this study adds evidence to the existing literature that the use of video analysis to confirm the occurrence of impacts and to correctly categorize them is highly beneficial to ensure reliability in future studies.

Submitted by Katie Conway

The age-associated decline in propulsive push off power generated during walking plays a central role in the reduction of mobility and independence in older adults. Previous work suggests that this population retains an underutilized propulsive reserve during normal walking that dynamometry assessments fail to effectively assess. This is especially notable when assessing plantarflexor mechanical output, which often yield implausible (i.e., ≥100%) values of ‘functional capacity utilized (FCU)’, most frequently defined as the ratio of the peak ankle moment during the push-off phase of walking to that during a maximum isometric voluntary contraction. Therefore, the extent to which we utilize our propulsive capacity, how utilization changes as we age, and the factors that govern utilization and maximum propulsive capacity remain unclear. Utilizing a feedback controlled, motor driven horizontal impeding force system and a novel maximum force condition which systematically increases applied force, we can find a participant’s maximum propulsive capacity. During this condition, we find that younger adults retain a reserve of 48% in terms of ground reaction force, 22% in terms of ankle moment and 43% in terms of ankle power, which may not be effectively predicted using dynamometry assessments. As an important first step, we present data showing that a more functional task, walking with horizontal impeding forces, could potentially more effectively assess propulsive reserves in younger adults.

Listed In: Biomechanics